(1) Field of the Invention
The present invention relates to the field of computer systems. More particularly, the present invention pertains to a computer system provided with a system for reading files containing data, such as an electronic mail system.
(2) Description of the Related Art
As it is well known, most modern computer systems are provided with the capability of electronically communicating with other computer systems for allowing users to share information. Electronic mail, for example, offers such capability of communicating by providing the means for transmitting, receiving, and processing user-generated messages between computer systems. Electronic mail, or e-mail, functions similarly to a post office mail system, by receiving letters from a sender and further transmitting these letters to an addressee. Electronic mail systems also provide features allowing other information to be transmitted from one computer system to another, such as files or other data typically referred to as enclosures. While typical prior art electronic mail systems have surpassed the capabilities offered by conventional post office mail systems, by providing capabilities for forwarding mail messages, responding to mail messages, opening messages, printing messages, removing enclosures (files) included with the messages, etc., such electronic mail systems suffer from several disadvantages.
One disadvantage of prior art electronic mail systems is that they typically require the use of a dedicated electronic mail application program for reading and otherwise processing messages. For example, in some circumstances the recipient of a message must read electronic mail documents with the same type of application that the sender used to create the document. Users of computer systems such as, for instance, Apple.RTM. Computer, Inc., located in Cupertino, Calif., may prefer to read AppleMail.TM. documents, which are documents created by an AppleMail application program (dedicated creator application), with an application program other than AppleMail. Such a preferred application program may be simply a text editor or a more sophisticated program, capable of translating AppleMail documents, such as ClarisWorks or BBedit. Similarly, users may desire to open or print a document created by a first application program (e.g., Microsoft Word) by using a second application program (e.g., WordPerfect).
Conventional computer systems such as Apple systems provide an application program such as MacLink.RTM. Plus/PC for translating files having a first format to files having a second format. For example, files having formats compatible to DOS operating systems can be translated into files compatible with the MacIntosh or Apple operating system. For more information related to the MacLink.RTM. translator please see MacLink.RTM. Plus PC user manual. Similarly, Apple Systems provide an application program called MacIntosh Easy Open to simplify opening documents created with programs that are not currently installed in the system's hard disk. The Easy Open application program recognizes different file types and uses built-in translators to help convert files and open them in an appropriate application that is present in the system. For more information related to the MacIntosh Easy Open, please see chapter 5 of the publication MACWORLD SYSTEM 7.5 BIBLE, 3rd Edition, published by IDG Books Worldwide, Inc. Present electronic mail systems, however, do not support the selection of a preferred mail reader application different than a dedicated reader application such as AppleMail reader in Apple systems and redirect an event to such preferred mail reader application. In electronic mail, and other application programs which transmit data, the sender does not necessarily know the capabilities of the recipient. In the traditional post office, all that is required is that the sender knows that the recipient is able to read. Similarly, electronic mail users should be able to use any type of electronic mail program, word processing or text editor that they choose, irrespective of that used by the sender of the data. This allows users to read and/or process any type of mail documents with a preferred application with which they feel more comfortable or which they find more appropriate for their particular goals.
FIG. 1 shows a block diagram of a prior art system with a second application program 6 processing an object 2 created by a first application program 1 (e.g. reading an electronic mail document). The object document 2 can be created by creator application program 1 in a remote computer system or the local computer system. The object document 2 has a creator type 3 `aaaa` which corresponds to the creator type `aaaa` of the creator application program 1. Computer systems such as the Macintosh.RTM. of Apple Computer.RTM. can identify an application program through the "signature" of the application. The signature is a unique four-character sequence such as `aaaa.`
Whenever an application program 1 creates a document, the application program 1 assigns the document a creator type and a file type. Typically, an application program sets its signature as the document's creator type 3. When a user double-clicks a document or selects it and chooses "Open" or "Print" from the Finder's file menu, a Finder 5 reads the creator field 9 of that file to find the document's creator type 3. Finder 5 is an application that works with the operating system software 4 to keep track of files and to manage the user's desktop display. After determining the creator type 3, Finder 5 searches for an application program with a signature corresponding to the same creator type as the one found in the creator field 9 of the object selected or clicked. When Finder 5 finds the application program 6, Finder 5 may launch this application program 6 or call the Process Manager to activate the application program. The Process Manager creates a partition of memory for the respective application program, loads the code into this partition, and performs some operations in preparation for launching. The Process Manager then returns control to Finder 5. For more information regarding Apple systems and identification of applications by signatures see the publication INSIDE MACINTOSH, MACINTOSH TOOL BOX ESSENTIALS (1992) available from Addison-Wesley Publishing Company. Similarly, conventional mail systems have associated mail information with an application program that created them by assigning to each mail document a signature or creator type corresponding with the signature of the creator application program which created that particular mail document.
The creator type of the creator application 1 and of the object 2 is used by the Finder 5 to determine what application, in a local system, can process an event associated with the received object 2. An event is defined as the means by which an Event Manager communicates information about user actions, changes in the processing status of the application, and other occurrences that require a response from an application. The Event Manager represents the collection of routines that an application can use to receive information about actions performed by the user, to receive notice of changes in the processing status of the application, and to communicate with other applications.
Typically, upon the generation of an event associated with object 2, such as double-clicking on a file in the Finder 5, the Finder 5 sends a request to the Operating System 4 which, in turn, references a table containing a creator. The table is stored in a non-volatile storage media or system memory storing all the 4-byte creator types or signatures of the applications that are present in the system. For each creator type in the table, a dedicated processing application program 6 is referenced. For example, when a request or event is sent to open a document that has the creator type `aaaa,` the Finder will determine whether the `aaaa` creator type is present in that table. Assuming that the creator type is present in the table, the Finder then references and alerts the dedicated processing application 6 that a request to open a document is pending. For example, assuming that the creator application 1 is an AppleMail application having the signature `aaaa,` the source object 2 will have the creator type `aaaa.` Upon receipt of an event associated with object 2, such as open document or print document, the Operating System 4 will forward the respective event to the dedicated processing application 6 which can be an AppleMail application or any application of the same type as the dedicated creator application program 1. The dedicated processing application 6 will then process the requested event allowing a user, for example, to read the object 2, in the case where the event associated with the object 2 is an open document event.
However, according to the system illustrated in FIG. 1, the user is typically not able to use a preferred local processing application such as e-mail reader or word processor, other than the dedicated processing application because the Finder 5 typically forwards the event associated with object 2 to the dedicated processing application 6 or a copy thereof. As such, it is desirable to provide a method and apparatus having the capability to forward events associated with an object created by a dedicated creator application to a preferred processing application, such that desired events associated to that object can be processed by the preferred processing application program.